Automatic Transmission Control System Developed for Toyota Mild Hybrid System (THS-M)

Environmental improvement is moving forward, due in part to the reduction of fuel consumption of automatic transmission(AT) vehicles as a result of social requirements in recent years and many measures have been implemented. Adoption of idling stop is a typical example introduced to reduce energy consumption while the vehicle is stopped to improve the urban environment. However, there are problems such as responsiveness and smoothness for an AT vehicle when the engine is stopped with the shift selector in “D” range.

To overcome these problems, a new start clutch control system has been developed using an electric oil pump installed in a simple hybrid vehicle called a mild hybrid. As a result, a smooth feeling starting performance is achieved by operating the system in combination with the engine and other systems. Additionally, low fuel consumption and a smooth driving feeling are achieved by expanding the regenerative braking area upon deceleration by ensuring optimum harmony of the lock-up clutch with the engine and electrical systems.

This paper gives the configuration, features, performance and effects of the AT control system that satisfies both requirements of high response and smooth feel, using the system installed on a mild hybrid vehicle.